1. Field
One or more embodiments of the present invention relates to a lithium battery.
2. Background
Lithium secondary batteries are used in portable electronic devices for mobile communication, such as personal digital assistants (PDAs) and mobile phones, as well as notebook computers, electric bicycles and electric vehicles. Lithium secondary batteries can have as much as twice the discharge voltage of a typical battery, and thus, lithium secondary batteries have high energy density.
Lithium secondary batteries produce electric energy due to oxidation and reduction reactions occurring when lithium ions are intercalated to or deintercalated from a positive electrode and a negative electrode. The positive electrode and negative electrode can each include an active material that enables the intercalation and deintercalation of lithium ions, and an organic electrolyte or a polymer electrolyte can be filled between the positive electrode and negative electrode.
For example, an oxide that consists of lithium and a transition metal and has a structure enabling intercalation of lithium ions may be used as a positive active material of a lithium secondary battery. Examples of such an oxide include lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), and lithium nickel cobalt manganese oxide (Li[NiCoMn]O2, or Li[Ni1−x−yCoxMy]O2).
A carbonaceous material, such as an artificial and/or natural graphite or hard carbon, and a non-carbonaceous material, such as Si, which enable intercalation and deintercalation of lithium, may be used as a negative active material.
The requirement of a battery having high-capacity has resulted in the development of various electrode systems. As a way to achieve high capacity, for example, overlithiated lithium transition metal oxide having a layered structure can be used as a positive electrode, and a silicon-based negative active material can be used as a negative electrode. Such an electrode system requires an excellent electrolytic solution having excellent high voltage characteristics due to its operation at high voltage.
Most non-aqueous electrolytic solution solvents used in conventional lithium secondary batteries have a low withstanding voltage property. When an electrolytic solution including solvents having low withstanding voltage property is used in a lithium secondary battery, during repeated cycles of charging and discharging, the solvents decompose to generate gas, and thus, internal pressure of the battery increases and/or a product of the decomposition may cause a polymerization reaction or may attach to the surface of the battery.
Accordingly, there is a need to develop an electrolytic solution that is suitable for a high-capacity electrode system at high voltages.